Whisk together 1 large free range egg, 1 tbsp balsamic vinegar 1 tsp sea salt. Add this to the butter and flour and, using two forks, gently toss through until the dough begins to come together. Add 1-2 tbsp ice cold water to bring the dough to a rough ball.

Thinly slice 1 large onion and break 1 head of broccoli into florets (around 300g).

Shred 400g cooked chicken and set aside.

Melt 25g of the butter in a large frying pan, add the onions and fry slowly for about 15 minutes or until softened and caramelised.

Add the remaining 50g of butter to the saucepan and allow to melt over a medium heat, add 2 tbsp flour and cook for 1 minute, whisking to combine.

Gradually add 350ml hot chicken stock whisking briskly until it thickens. If it goes a little lumpy, don’t worry; just whisk vigorously until it becomes smooth.

Reduce the heat and simmer for 3–4 minutes. Season with a generous pinch of salt, black pepper and add 1 heaped tsp english mustard. Pour in 150ml single cream and stir through, allowing to cook for a further minute.

Steam the broccoli in a metal steamer until al dente (i.e. not completely tender) then drain and refresh in a bowl of iced water.

Add the broccoli and 400g cooked, shredded chicken to the sauce and stir well.

Transfer the mixture to an ovenproof baking dish, 20cm/8" diameter and 5cm/2" deep.

Roll the pastry out onto a floured work surface large enough to fit the top of the dish.

Brush the edges of the dish with a little beaten egg and place the pastry on top of the pie. Brush with a little more beaten egg and cook in the oven for 25 minutes until the pastry is puffed and golden.